1. Field of the Invention
This invention relates generally to rotors for rotorcraft, and more particularly to a rotor that can be folded so that the rotorcraft may be more easily stored, and may also be driven as a land vehicle.
2. Description of Related Art
The following art defines the present state of this field:
Weiland et al., U.S. Pat. No. 4,028,000, teaches a resilient drive for a helicopter rotor blade. The rotor blade is pivotally supported on a stub shaft which is in turn supported on the rotor hub. A shoulder projects from the rotor blade and a rectangular hollow frame is fixed to the stub shaft. The shoulder projects into the hollow frame. Threaded means acting through resilient means holds the first and second means in selected pivotal adjustment with respect to each other but the resilient component thereof permits sufficient slight lead lag movement therebetween as to effect damping of the lead lag mode of the rotorblade. The adjustment capability permits sufficient adjustment of the blade with respect to the hub to ensure desired balance between the several blades of a given rotor.
Bernard, U.S. Pat. No. 4,268,222, teaches a folding rotor having a star-shaped hub with arms flexible in the direction perpendicular to the plane of the star-shaped hub. A housing is detachably mounted on the rigid central part of the rotor hub. The housing carries elongate supports on a side. The free end of each support is detachably joined to the upper part of the folding shaft of the corresponding blade. This folding shaft can consist of a spindle replacing a link shaft between the foot of the blade and the corresponding arm of the hub.
Lovera et al., U.S. Pat. No. 4,369,019, teaches a helicopter rotor having elastomer joints, in which each blade is connected to a rotatable hub by means of a yoke constituted by a single U-shaped piece and mounted through a relative aperture provided in said hub; each yoke being connected to a transverse arm outwardly bordering said aperture, by means of a U stirrup embracing the relative said arm and provided with two overlying appendices extending outwards and having two surfaces inclined towards the other and acting as stop surfaces for two rocker arms constituting a device for controlling the flapping movements of said blade; said two rocker arms being mounted rotatable in a substantially vertical plane passing through the axis of the relative blade and being supported by a lever for controlling the pitch of this latter.
Bauer et al., U.S. Pat. No. 6,126,398, teaches a rotor blade for a bearingless rotor of a helicopter. The rotor includes a lift-generating airfoil blade, a flexbeam connecting the airfoil blade to a rotor head, and a control sleeve enclosing the flexbeam. The junction between the flexbeam and to the airfoil blade is a separable junction to allow the airfoil blade to be folded in a simple manner while maintaining a high lead-lag stiffness and reduced structural height of the junction. The junction is formed by two connection arms arranged side-by-side in the lead-lag plane of the rotor blade. Preferably, the two connection arms extend from the inboard end of the airfoil blade and receive the head of the flexbeam therebetween lying in the lead-lag plane. A connecting fixture connects the connection arms to the flexbeam head using fasteners such as bolts that are spaced laterally from each other at a spacing distance of at least 1.3 times the maximum width of the torsionally flexible portion of the flexbeam.
Muylaert, U.S. Pat. No. 6,213,712, teaches an improved blade positioning mechanism for folding a helicopter blade attached to a pitch control housing that permits a controlled folding of the main rotor blade. The invention also folds the main rotor blade while the blade remains attached to the pitch control housing, thus eliminating the need to rebalance the blade.
Davis, U.S. Pat. No. 6,783,327, teaches blade fold hinge units attachable between each helicopter blade and its hub attachment point, while maintaining continuity of mechanical connection of each blade to its hub portion. A two portion hinge unit has a first portion for blade attachment and a second portion for hub attachment. The first and second portions are hinged via a transverse pin to enable blade drooping downward, before or after a blade is pivoted to an aft position for helicopter storage or shipment. Upon aft pivoting of a blade, undesired further pivoting or knuckling of the hinge unit relative to the hub is prevented by addition of a lock link. After blade folding, the blades may be suitably fixed in position adjacent the aft portion of the helicopter body.
Watson, U.S. Pat. No. 4,436,483, teaches a helicopter rotor that includes a powered blade fold mechanism adapted to move a rotor blade between a spread operational position and a folded position and at least one lock pin to lock the blade in its spread position. The mechanism includes a rotary power source and a mechanical linkage having an over-center position and adapted so that energization of the power source in one direction moves the linkage through the over-center position to withdraw the lock pin and fold the blade, and energization in the other direction moves the blade to the spread position and re-inserts the lock pin automatically as the linkage moves back through its over-center position. Lock means may be provided to lock the blade in pitch and, in one embodiment particularly adapted for use in an articulated rotor, the lock means includes pitch, flap and lag locks.
Martin, U.S. Pat. No. 4,466,775, teaches a helicopter rotor having a rotor hub and a plurality of rotor blades. The rotor includes for each blade a blade fold mechanism comprising a reversible rotary power source and a rack and pinion mechanism adapted to operate one or more lock pins and to fold the blades between an operational spread position and a folded position.
Seghal et al., U.S. Pat. No. 5,211,538, teaches a method of folding the main rotor blades of a helicopter for storage in which blade supports are removably attached to the nose and tail of the fuselage of the helicopter. A first and second main rotor blades then are aligned with the longitudinal axis running from the forward blade support to the aft blade support. The first and second blades are placed upon, and restrained from rotation in, the blade supports. Then the first and second blades are permitted to fold about the rotor assembly of the helicopter by releasing a locking member of each blade.
Other patents of interest include Muylaert et al., U.S. Pat. No. 6,860,450, Mondet et al., U.S. Pat. No. 6,485,261, Papadakos, U.S. Pat. No. 2,815,820, and Mondet et al., U.S. Pat. No. 6,752,596. These and the other above-described references are hereby incorporated by reference in full.
The prior art teaches various forms of folding rotors. However, the prior art does not teach folding rotors that are connected through a linkage including a resilient. The present invention fulfills these needs and provides further related advantages as described in the following summary.